Depth imaging technology has advanced dramatically over the last few years. Pixels in a depth image indicate calibrated depth in the scene, rather than a measure of intensity or color. Depth images may allow for more accurate detection of objects such as human beings. Further, detection or localization of a human head may aid the detection of other human body parts in an image such as shoulders, torso, arms and legs, and so forth.
Most of the current approaches to human head location, like color-based methods and face detector based methods, utilize either color or grayscale intensity information. Moreover, face detection techniques are of no avail when the subject is not facing the camera. While, skin color detection techniques may be useful for locating other parts of the body, such techniques have difficulty adapting to varying illumination. Recent attempts at human body part detection based only on depth information are problematic when a subject's hands are closed and/or when the subject's head is partially or fully occluded by another body part (e.g., as may occur when a subject is bending forward). In addition, to train object detectors, conventional depth-based techniques tend to require detailed 3D human pose images that are difficult to acquire.